Oiled concrete roadway.



E. M. CHADBOURNE. UILD CONCRETE ROADWAY.

APPLIoATIoR num AUG. 4. 19m.

956,940. Intentan May 3, i910.

f UNITED STATES PATENT oEEToE. A

EDWARD M. CHADBOURNE, OF SAN FRANCISCO, CALIFORNIA.

OIL-ED CONCRETE ROADXVAY.

A Application e August 4, 1909. Serial No. 511,159.

To all whom i1'- may concern:

Be it; known that l, Enwann M. Cuan- BoUnNr., citizen of the. United States, residinf.,r in the city and county of San Francisco and State of California, have inented new and useful Improvement-s in Oiled Concrete Roadways, of which the following is a specifiCOD. I

This invention relates to highway construction, and pertains especially to an oiled reinforced cement macadam road.

The object of the invention is te provide a road, street or way which is strong structurally, monolithic in character, and with a Wearing cushion on the surface which is dustless, permanent, and vrequiring little, or no expense for maintenance or repair.

The special object of the present invention is to so construct this roadway that this surface cushion, which is made np of a mi.\: ture of oil and screenings, is firmly anchored to its underneath foundations; and in the c'onstruction of this roadway provision is made to prevent the downward percolation 0f the oil, so that in the end a true asphaltic surface for the roadway is produced.

The invention consists of the parts and the const'ruction and combination of pa rts as Aso hereinaftermore fully described and elaimed, having reference to the. accompanying draw ings, in which- The figure is a sectional view in perspective, showing the method of enustructing a roadway accordingr to the invention.,

In the practice of the invention. the, road is graded, crowned and laid out, according lo surveyed' lines, and suit-ably prepared until it isCompacted to a smooth lhard surface. This preparation usually comprises the harrowing of the'road until aboutI two inehes ot' the surface is loose. lt is then watered to a oint of saturation and allowed to dry until it is no longer sticky or plasticwhereuponit is rolled or Itamped until the surface is smoothl and hard. Next the rein fort-ing fabric 2 is laid on the prepared sub-grado This reinforcing fabric consists preferably 0f a square mesh, with redrawu steel wires running longitudinally and laterally' and suitably connectedby clips or locks' It. This fabric preferably has a (xli mesh. and is suitably supported ou the sub-grade so that it. will lie about one inch above. the subgrade. This support for the reinforcing fabric 2 is here, shown as comprising a series of metal strips 4 punched ont. to Vform open- Specicetion of Letters Patent.

Patented May 3, 15H0.

ings 5, and having base flanges bent in ou.

posite directions, so that it. will stand up edgewise on the sub-grade and in appearance be like. an inverted T. rlhese strips extend at suitable intervals across the roadway, and also act as a reinforcement, since, the openings :3 permit: of a perfect bond of the concrete T on all sides of the reinforce and metal support.

After t e reinforcing .fabric is laid, the cement macadam 7 is placed as 'ordinary concrete, usually about four; inches in thickness, and comprises proper mixtures of cement, sand, and crushed rock or gravel. The, crushed rock or ravel should be clean, and of sucn sizes as will pass through a two inch ring. This cement. macadam 1s thorough! mixed by a rotary concrete mixer, and sul cient water is added to produce a plastic mixture, in which condition it is deposited on the prepared sub-grade and qiread evenly thereover.

Before the cement. macadam concrete layer 7 has set, and while. it is still in a )lastic condition. itis covered with a course oi clean hard rock of about ege size, as represented at 8. This course. of theavy rock is spread evenly over the surface of the concrete and will become partially embedded in the same; and when the concrete is set, this course of rock S, will form au integral part of the concrete foundation, with the points projecting about an inch above the surface. of the underneath concrete body in which the rodi is embedded. This roughened dressing S is one of the important features of this ineention, because the interstices which are formed between the projecting pinnaeles constitute little reservoirs of an inch or so in depth in which the heavy asphaltic oil which is later applied will collect. Y

"hen the cementmacadam and its rough surfacing S are thoroughly set and dried out, so that the course of heavy rock is vlimpid, .nd while at this temperature it is spread and brushed-mer the surface of the cement nlaeadaui, care being taken thatI all the intersliees in the surface are thoroughly tilled. li' it were not for the pockets or reservoirs formed by the rotruding points 8 the oil would run oit o the foundations,

iti)

Q Acriceto and thus defeat oneessential feature of the invention. Immediately after the oil has been applied. a layer of ne screenings is spread over the 4surface to a depth ot about one inch. This layer of screenings sinks down intothe oil pockets and absorbs the oil. This layer of oil-saturated screenings, represented at l0, is then rolled with a six ton. or heavier roller until it is con'ipacted into what is. in actual etlcct, an asphaltic surface imilar to the standard asphaitic pavements of to-day. v

On accountof the impervious character of the concrete, the oil in the small reservoirs or openings formed between the rocks of the layer 8 is within less than two inches of the surface, so that the oil deposited in these pockets has a chance to become thickened by evaporation or oxygenation, and the absorption vof the heavy asphaltic residuum by the fine screenings gives durability and hardness to the surface. i This desired change in the oil would not take place if the underneath foundation were porous so that the oil could sink through to three or six inches in depth.

In my construction the Oil is kept and maintained near the surface, so that its whole bonding and elastic value is preserved and utilized.

The course of egg-sized rock 8 which is embedded in the top of the concrete is also in some cases' part of the wearing surface,l

projecting up through the final asphaltic top dressing l0, and preventing slipping of horses" `fleet on the asphaltic surface.

It is readiy seen that the top layer of the asphaltic oil and screenings 1() is held very rigidly to the top of the concrete foundation, both b f the adhesion of the oil to the concrete an the top course 8, and the lock or bond formed by the pockets between the rocks of the course 8.

A roadway of this character has all the desired requisites of permanency provided by the reinforccdement macadam foundation. It has all the elastic qualities of, and much greater durability than, the ordinary bitnminized cr asphalt street or roadway. And furthermore, itcan be laid down for from '25% to 50% cheaper, as practice has shown, than-the ordinary asphalt or btu minized road.

I Ia rin g thus described my invention, what I claim and desire to secure by Letters latent is- 1. 'l'he method of roadway construction which consists in preparing a s uitable subgrade and spreading a suitable layer of concrete thereover, and while this concrete is still in a plastic condition covering it with coarse rock thereby forming pockets in the top surface thereof, alltm'ing the concrete with its rock coating to set into a solid structure. oiling the surface of the foundation so formed, so as to till the pockets with oil of asphaltic base, then applying a layer of screenings to the oil sutlicient. to take up to pressure.

1).. The method of roadway construction which comprehends preparing a suitable t concrete--foundation for the roadway, which foundation comprises a concrete slab extending over the roadway, and while this concrete i-= lstill in a plastic condition` forming pochi-ts, of approximately an'inch or moniu depth on its surface, filling these pockets with a heavy asphaltic oil and then applying tine screenings to absorb the oil in the pockets, and rolling the plastic mixture se formed to compact the same in the pockets.

3. The method of constructing a cement macadam roadway consisting ot' placing a layer of reinforced concrete on the'sub-grade and while in a plastic condition providing its surface with oil retaining` pockets, pour,- ing a coating of heavy asphaltic oil over the surface to till the pockets, and spreading a layer of tine scrnings over the oil to absorb the oil.

4. The method of roadway construction which comprises the following steps in substantially the following order, to-wit: first, the preparation of a suitable sub-grade; -second, the laying of a suitablel concrete slab over this sub-grade and forming in the top of this slab pockets of approximately an inch or lnore in depth; third, filling these pockets with 'a heavy oil, which oil is normally in condition to be absorbed at ordinary temperatures; and fourth, spreading a layer of screenings over the. oiled surface ing approximately an inch in thickness, and causing'the screenings to sink into the oil in the pockets and lill the pockets.

In testimony whereof 1 have hereunto set my hand in the presence of two subscribing witnesses.

EDlVARD M.l CHADBOURNE.

Witnesses: A

CHARLES EDELMAN, C. C. COOL the oil, and then subjecting the oiled surface ot' the road-bed, said layer ot' screenings bev 

